I'm not sure experts even exist. After all, if you think about one topic that you should know the most about - your own self - there are probably still some things that people could tell you about yourself that you didn't realize. I think the true value (or benefit) of expertise is the ability to filter the information.
For example, one of the books I'm reading right now is, "Playing to Win: How Strategy Really Works" by A.G. Lafley and Roger Martin. (You can check it out here). For anyone looking to develop a strategic plan for their business, this book is a great resource. In fact, I might even say, it's a great benchmark for any business to use. However, even with Lafley's wild success as leader of P&G, this book is largely focused on how he made P&G flourish. If you are not a big corporation like P&G, it's likely that a good number of the concepts will be over the top. However, if you take the time to filter the information and extract the nuggets of information that apply to your own business, you can reap tremendous value.
Take another example - the last time you went to the doctor or the last time you took your car in for repairs. You kinda had an inkling about what was going on, but you relied on the "expert" to share his education and experience to diagnose the problem. Likely, you took the information and ran it through your own filter and decided on next steps. Sometimes that means following advice, sometimes that means getting a second opinion, which in itself says no one is the expert!
Filtering. The point here is that there are many sources of information. Many "experts" spouting their mantra. Sometimes that information sheds light on a totally new way of approaching things and that leads you on a new path. Sometimes you put the information through your filter and realize the current path is the right one. The key is to remain open to new information or new approaches - just use your filter to determine whether it applies to your unique situation. In the end, the true value of expertise is not blind trust, it's filtering.
So who's trying to be an expert now? Not me, really, just sharing something else for your own filter process!